Dropped Third Strike - Interference?

[aschramm]

Last night I had a U14 game with FED Rules. R1, less than two outs. R1 attempts to steal second base, pitch is a dropped third strike. Batter starts running toward first, even while I'm announcing "batters out" from B position. Play continues, catcher throws to first even though he doesn't need to.

On plays like this, is there any rule that could be applied for offensive interference, since the retired batter's actions caused the defense to make a play that they didn't have to, instead of focusing on R1, who is now R2? My thought would be that you can't call an out on offensive interference, since the batter is already out. Or is it just the defense's fault that they don't understand the ruling on this play?

There was no controversy with this play, I am just curious as how I could handle it if defensive coach yells for interference by the retired batter.

Thanks!